From c4c4b3318a89c0a7548040f7182fb043704e230f Mon Sep 17 00:00:00 2001
From: Mike Morris <michael.patrick.morris@gmail.com>
Date: Tue, 30 Sep 2014 17:42:27 -0400
Subject: [PATCH] log CGLErrorString for CGLChoosePixelFormat, enable OpenGL
 multithreading

https://developer.apple.com/library/mac/technotes/tn2085/_index.html
---
 common/headless_view.cpp | 8 +++++++-
 1 file changed, 7 insertions(+), 1 deletion(-)

diff --git a/common/headless_view.cpp b/common/headless_view.cpp
index 61531bfd6..10888f7a7 100644
--- a/common/headless_view.cpp
+++ b/common/headless_view.cpp
@@ -20,7 +20,7 @@ HeadlessView::HeadlessView() {
     GLint num;
     CGLError error = CGLChoosePixelFormat(attributes, &pixelFormat, &num);
     if (error) {
-        fprintf(stderr, "Error pixel format\n");
+        fprintf(stderr, "Error pixel format: %s\n", CGLErrorString(error));
         return;
     }
 
@@ -30,6 +30,12 @@ HeadlessView::HeadlessView() {
         fprintf(stderr, "Error creating GL context object\n");
         return;
     }
+
+    error = CGLEnable(gl_context, kCGLCEMPEngine);
+    if (error != kCGLNoError ) {
+        fprintf(stderr, "Error enabling OpenGL multithreading\n");
+        return;
+    }
 #endif
 
 #if MBGL_USE_GLX